first-javascript/failai3.js at master · plukenis/first-javascript · GitHub

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const fs = require("fs");

function readFile(name, options) {
    return new Promise((resolve, reject) => {
        fs.readFile(name, options, (err, data) => {
            if (err) {
                reject(err);
                return;
            }
            resolve(data);
        });
    });
}

console.log("pradzia");

let allData = "";

let p = readFile("a.txt", {
    encoding: "utf-8"
});
let p1 = p.then(
    data => {
        console.log("perskaiciau faila a.txt");
        allData += data;
        return readFile("b.txt", {
            encoding: "utf-8"
        });
    }
);
let p2 = p1.then(
    data => {
        console.log("perskaiciau faila b.txt");
        allData += data;
        return readFile("c.txt", {
            encoding: "utf-8"
        });
    }
);
let p3 = p2.then(
    data => {
        console.log("perskaiciau faila c.txt");
        allData += data;
        return readFile("d.txt", {
            encoding: "utf-8"
        });
    }
);
let p4 = p3.then(
    data => {
        console.log("perskaiciau faila d.txt");
        allData += data;
        console.log(allData);
    }
)
let p5 = p4.catch(
    err => {
        console.log("nepavyko perskaityti failo");
        console.log(err);
    }
);

console.log("pabaiga");